This Program Project will study progression and regression in femoral, coronary, and carotid artery lesions in 160 men with premature atherosclerosis. A clinical study will be modelled on the Coronary Drug Project; smokers will be segregated from non-smokers. Image processing will be used to measure lesion change in femoral and coronary angiograms plus carotid and femoral ultrasonograms. A clinically useful ultrasound imaging instrument will be calibrated against angiograms. Image averaging will be applied to coronary angiograms. Spatial reconstruction of vessel lumen will be obtained from femoral angiograms. Lipid phase diagrams of lesions showing progression will be compared with those showing regression. A tomographic procedure for vessel branch junction area reconstruction will be developed. Computer modelling of branch junctions will apply Navier-Stokes equations to flow and oxygen transport. This will be followed by bench testing of flow models. Oxygen tension in branch junction walls will be measured with microelectrodes. Acute and chronic induced branch junction lesions will be studied in human placentas. Spontaneous branch junction lesions in canine coronary arteries will be studied.